Insulated storage tank



Sept. 17, 1963 c. D. DosKER 3,104,025

INSULATED STORAGE TANK Filed Jan. 6, 1961 2 Sheets-Sheet 1 Cornellus D. Dos ker- QW 22./ #QW Z Z ATTorneus Sept. 17, 1963 c. D. DosKl-:R

INSULATED STORAGE TANK 2 Sheets-Sheet 2 Filed Jan. 6, 1961 INVENToR. Cornehus D. Dosker Y A++orneqs United States Patent 3,104,025 INSULATED STRAGE TANK Cornelius D. Dosker, Louisville, Ky., assignor to Couch International Methane-Limited, Nassau, Bahamas, a corporation of Bahamas Filed Jan. 6, 1961, Ser. No. 81,004 7 Claims. (Cl. 220-1S) This invention relates to an insulated structure for housing fluids and liquids having temperatures differing widely from ambient temperature and it relates more particularly to an insulated storage tank for housing a liquelied gas such as liquefied natural gas.

This invention will be described with reference to the ship transportation of liquefied natural gas in large volume from a source of plentiful supply to an area Where natural gas deficiencies exist. It will be understood that the concepts described are not limited to the storage and transpoi-tation of liquefied natural lgas but will have application to the storage and/ or transportation of other extremely cold liquids and also to the land storage of such liquefied gases in large volume.

In lthe storage of a liquefied -gas in large volume, it has been found to be impractical to construct a container wherein the liquefied ygas is maintained under high pressure so as to enable the liquefied gas to be retained at ambien-t temperature. Thus, large capacity tanks for the storage or transportation of liquefied natural gas are designed for housing the material at 'about atmospheric pressure and preferably under slight positive pres-sure suiiicient to minimize the danger of air -being drawn into the tank.

At about atmospheric pressure, liquefied natural gas has a boiling point temperature within the range of 240 t F. to about 258 F., depending upon `the amount of heavier hydrocarbons present in the liquefied gas. Other liquefied gases have similar low boiling point temperatures such as -70 F. -for carbon dioxide Iand a temperature of about --320o F. for air, nitrogen, helium and the like.

In order to reduce heat loss into the cold liquid to minimize vaporization during storage and transportation, it is desirable to provide 'a thermal insulating barrier between the ambient `atmosphere and the liquefied gas. The capacity of the tank, the wide temperature differential and the effect of the cold on the metal-s employed in the ship structure and in the tanks present a number of complex and unique problems with respect to the construction of the insulated storage facility.

Steel plate ordinarily employed in the construction of a tank or the hull of a ship has been -found to be incapable of use where the steel is exposed to a temperature below -l00 F. because such metals lose their ductility and become embrittled at such temperatures. As a result, when the liquefied gasvis to be transported or housed within the hull of a ship, it is desirable to house the liquefied -gas in la separate tank yor shell tformed of a f-uid impervious, temperature-insensitive material such as aluminum or alloys o'f aluminum, copper, stainless steel, or other austenitic steels which retain their yductility and strength at the low temperatures o-f the liquefied cargo. It is desirable also to insulate the container` from the steel hull of the ship or the housing in which the separate storage tanks arearranged.

To lthe present, attempts have been made to make u-se of an insulation system which not only minimizes heat loss to the liquid and transmission of cold from the liquid to the steel walls of the ship but which also comprises a barrier to the passage of fluid in a manner to present a second line of defense which prevents the passage of the liquid intocontact with the steel walls in the event of failure or escape of liquid from the separate insulated containers. For this purpose, use has been madeof panels of balsa Wood or quippo joined one to another in sealing relationship across the inner sur-faces of the ship structure defining the ships hold to insulate the ship structure against the passage of iliquid and in which `a back pressure principle may be developed to militate against the penetration of liquid through the insulation to the steel wall of the ship. In the back pressure principle, penetration of the liquid will continue through the insulation layer until it reaches a point in the insulation where the temperature is at a level at which the liquid cannot remain in the liquefied state. Diffusion of the vapor that Vis formed in a direction back through the insulation layer is blocked by the wall of liquid penetrating into the insulation and diffusion in the opposite direction is blocked by the wall upon which the insulation is mounted. Thus the vapor is entrapped 'within the pores lof balsa wood. If the permeability of the vapor through the pores is such as to prevent the escape of vapors at a lrate faster than the vapors are being introduced from the liquid, a vapor pressure Will build up to prevent further penetration of the liquid into the insulation layer thereby to maintain an insulated space.

While it is desirable to provide a second line of defense against penetration of -the cold liquid to the steel Walls of the ship, it has been found that the separate tanks can lbe constructed in a manner to avoid the escape of liquid such that the need for a costly second line of detense can be avoided. It therefore becomes an object of this invention to provide a less expensive insulated structure for use in the storage and transportation of cold liquids, such as liquefied natural gas.

A further object 4is to produce and to provide a method of producing an `insulated structure of the type described which is formed of loW cost and readily available materials and which can be installed in a simple and efiicient manner to provide a low cost insulation system.

More specifically, it is an object of :this invention to provide a system for the storage and transportation of extremely cold liquids wherein the insulation embodies low cost and readily available materials which can be advantageously combined for the safe and economical storage and transportation of liquefied natural gas.

These and other objects and advantages of this invention will hereinafter appear and for purposes of illustration, but not of limitation, an embodiment of the invention is shown in the accompanying drawings, in which- FIG. 1 is aschematic sectional elevational view of a ship embodying the features of this invention for the storage of liquefied gas in large volume in the insulated hold of the ship; g

FIG. 2 is a cross-sectional elevational view of a fragmentary portion of the ship structure illustrating .a preferred embodiment of the invention;

, FIG. 3 isa sectional view showing a means for mounting the panels for independent movement within a supporting frame; f

FIG. 4 is a sectional view taken along the line 4 4 of FIG. 5;

FIG. 5 is an elevational view showing la segment of the paneled insulating Wall, and

FIG. 6 is a sectional view of a panel employed in the practice `of this invention.

As shown in FIGS. l and 2, there is provided an insulated structure represented by a ship or barge 10. The structure is provided with storage tanks 12 and 14which, under conditions of use, may be filled with a liquefied natural gas. To insure that the tanks will be self-sufiicient under -the conditions existing when filled with thecold cargo liquid, it is desirable that lthe tanks 12 and 1`4be constructed' with sufiicient wall thicknessof a temperahigh nickel steels, which materials are capable of withstanding the cold temperatures without loss of strength 01' ductility as would otherwise characterize ordinary steel plate of which the ships hull is constructed.

In the preferred practice of the invention, the ship or other transportation means is fabricated with an outer hull having side walls 16 and 18, a bottom wall 20 and a top deck 22. To protect the ships hull from the cold of the liquid, while at vthe same time strengthening the ship, it is desirable to construct the ship with an inner hull spaced from the outer hull as presented by the walls 28 and 30. A plurality of cross brace members 34 in the form of girders, I-beams and the like are secured to adjacent surfaces of the hull for purposes of strengthening the hull structure and also to deline wing tanks therebetween.

Having briefly described the ship structure and the tanks mounted within the hold space of the ship, the latter of which is defined by the inner hull, reference will now be made to the concepts of this invention for mounting low cost insulation within the inner hull to provide an insulated hold space in which the tanks are mounted preferably without attachment directly to the ship structure so as to enable movement of the tanks relative to the ship in expansion and contraction while still stabilizing the position of the tanks within the insulated hold space.

The insulation section mounted adjacent the inner surface of the inner hull 28 and 30 comprises a plurality of vertically disposed, laterally spaced apart furring strips 38 secured, as by means of Nelson studs 40 or other conventional fastening means, to the inner hull. 'In a typical construction, the furring strips 38 will be in the form of two by four lumber arranged in pairs 39a and 33h on 3 foot centers with the two by four in each pair being about 12 inches apart.

Each pair of furring strips 38 is provided with a frame member 42 arranged midway between lthe furring strips yand spaced inwardly therefrom. The furring strips and the frame members are interconnected by cross brace members 44. Again, in a typical installation, the frame members will comprise two by six lumber spaced about l2 inches inwardly from the furring strips and connected thereto by the cross brace members illustrated as dowel pins 46 and `48 extending from the frame members to the furring strips at angles of about 67 with the face of the frame members. The cross brace members are vertically spaced apart on about 12 inch centers firmly to support the frame members in spaced parallel relation with the furring strips and the wall 30 and 28 on which they are mounted.

The frame members 42 are adapted to support thin panels 50 of a structurally `strong and dimensionally stable, low cost material arranged in end-to-end and in side-by-side relationship to form a substantially continuous siding or wall defining the storage space in which the tanks 12 and 14, etc. are mounted. It is preferred to make use of plywood panels, but use can be made of` metal sheets, plastic sheets or combinations or laminates of metals, plastic and wood. The panels 50 are dimensioned to have a width corresponding to the spacing between the frame members. For example, in the illustrated modification, the panels S would have a width of 3 feet and a length of a conventional dimension such as 6, 8 or 12 feet. The lateral edgesy 50a and 50h of the panels are adapted to overlap the frame members to enable attachment thereto, as by nails, screws or the like, but it is preferred, because of the expansion and contraction problems due to extreme temperature change, to mount the panels as floating members free of the supporting frame members. For this purpose, as shown in FIGS.

4 and 5, theoverlapping edge portions ofthe panels are i shown in FIG. 3, each frame member 42 is provided with a cover strip 54 secured as by means of a bolt and nut assembly 56 to the frame member with a spacer 58 in between to space the cover strip by an amount corresponding to the thickness of the panels 50 iirmly to grip the edges of the panels between fthe cover strip 54 and the frame member 42. Thus, the panels, which will be exposed to extreme temperature change of from about F. when installed to about 250 F. when the tanks are iilled with liquefied natural gas, will be free to move relative to fthe supporting structure in response to expansion and contraction but without becoming disengaged from the supporting structure.

For this reason, the frame members 42 and the facing strips 54 are deemed to have a width greater than the amount of contraction calculated to take place in the panels upon reduction in temperature so that the edges of the panels will, at all times, be retained between the frame members yand cover strips, although the edges of the panels might be spaced one from the other in the assembly.

As illustrated in FIG. 5, similar cover strips 60 may be arranged to extend horizontally between the vertically disposed cover strips S4 with a vertical rspacing `between the horizontally disposed cover strips 60 corresponding -to the lengths of the panels to overlap or cover the meeting edges of the ends of the panels. These horizontally 4disposed cover strips 60 can be secured, asbyboiler plugs 62, to the supporting walls 30 or 28. The corner sections where the cover strips 60 and the cover strips 54 meet should be sealed ofi with a cover plate 64 more or less to conceal the joint and to provide some semblance of a temporary uid barrier.

It is desirable resiliently to urge the cover strips in the direction frictionally to engage the surfaces ofthe edge portions of the panels disposed between the cover strips 54 and the vframe members 42. For this purpose, the spacer 58 would be of lesser thickness than the panels and tensioning means 66 would be introduced continuously to urge the cover strip 54 outwardly in the direction towards the frame member 42 to grasp the edge portions of the panels therebetween. One such resilient means illustrated in FIG. 3 comprises an elongate bolt member 56 having its head 68 received within a recess in the front face of the cover strip and wherein the holt member extends slidably through an opening 70 in the frame member. The resilient means in the form of a spring 72 is positioned with one end bearing against a nut 74 on the end of the bolt while the other end bears against the back side of the frame member constantly to urge the bolt and the cover strip 54 in the outwardly direction.

`Further to provide I.a barrier against the penetration of cold liquid through the formed siding, a thin membrane of metal, plastics, or other uid and vapor impervious material, as represented by a film of aluminum, stainless steel, copper, polytetrauoroethylene, polyesters, resinous treated plywood and the like can be incorporated as an inner ply and preferably as a `face ply on the panels 50 and the sealing strips 54 and 60 or else as a continuous membrane covering the assembled panels. The feature of using an outer protective metal iilrn is shown to best advantage by the numeral 76 in FIG. 6.

In a specific embodiment of the invention (see FIG. 2), use is madeof a combination type of insulation construction wherein the bottom wall of the storage space is formed of a relativelythick layer 80 of thermal insulating material, preferably characterized by structural strength and dimensional stability, such as balsa wood panels or quippo. It is desirable` to make use of insulation of this character for Ause in support of the tanks out of contact` with the ship structure.

When a ooring of structurally strong and dimensionally stable material is employed, it is possible to incorporate therein means for stabilization ofthe` position of the tanks while still permitting movement of the tanks relative to the ship structure responsive to expansions and contractions in the metal container due -to temperature change. One such stabilization means, illustrated in FIG. 2, comprises the use of keys SZ extending downwardly from the bottom wall of the tank in radial alignment with the center theero-f as representative of the stabilized position for receipt in sliding engagement in corresponding keyways 84 provided in the surface of the insulated flooring. Such key and keyway construction stabilizes the position o-f the storage tank within the insulated space to obviate uncontrolled shifting movement of the tank responsive to the pitching and rolling movements of the ship or like housing while still leaving the tank free to expand or contract. When such flooring is employed, the lower edge of the lowermost panel 50 will be adapted to rest upon za horizontally disposed frame member 86, such as a two by four or other strong structural material.

There will be a space S8 between the wall or siding formed of the panels 50 and the inner surface of the inner hull. Within this space 88 there is placed various types of low cost thermal insulating material 'adapted to insulate the hull of the vessel against the cold of the liquid in storage while, at the same time, minimizing the transfer of heat from the ambient atmosphere to the liquid in storage to cause vaporization thereof. The insulation used for insulating the space 88 can be selected of a large variety of materials, such as finely divided cork, vermiculite, silica powders, glass or rock wool insulation, `diatomaceous earth and the like.

When -a continuous membrane lining o-f a cold-resisting metal such as an aluminum Kalloy `or stainless steel is laid over, and supported by, the assembled thermally insulated panels and insulated bottom wall, there results an insulated container for liquefied gases which necessitates no self-suicient storage tanks such as storage -tanks 12 and 14 described above. The membrane lining itself can act as the storage container, the weight of the liquid being taken by the insulated flooring andthe assembled insulated panels.

It will be apparent from the foregoing that I have provided la simple and inexpensive construction for the eilicient and economical insulation of a large storage space used for housing one or more tanks of large dimension for the storage of a material lhaving a temperature differing widely from the ambient temperature. While no attempts have been made specifically to embody a second line of defense to hold back the transfer of liquid which might accidentally be released kfrom the storage containers, it will be apparent that, in the construction defined, at least a temporary barrier will still be present to provide some factor of time in which to take care of |any emergencies which might develop.

It will be understood that changes may be made in the details of construction, larrangement and oper-ation, without departing from the spirit of the invention, especially as defined in the following claims.

I claimt 1. In the construction of an insulated space of large dimension for housing one or more containers iilled with a material having a temperature differing widely from ambient temperature, an enclosure dened by a bottom wall and vertically disposed walls, spaced apart furring strips iXed to the internal surfaces of the vertically disposed walls of the enclosure in which the furring strips are arranged in laterally spaced apart pairs with each of the furring strips in each pair being laterally spaced apart one from the other, frame members spaced inwardly from the furring strips and connected to the furring strips by cross brace members in which a frame member is provided for each of the pairs of furring strips and in which each frame member is connected to a pair of furring strips by horizontally disposed dowel pins extending outwardly from the frame members to the furring strips, thin panels of a structurally strong material arranged in end-to-end and in side-by-side relation and supported by the frame members to form a continuous siding in spaced relation with the enclosure walls to define a storage space for said containers, cover strips confronting the inner surfaces of the panels to overlap the adjacent edges and conceal any opening therebetween, and insulation material in the space etween the siding and the enclosure walls.l

2. An insulated structure as claimed in claim l in which the panels are dimensioned to have a width corresponding to about the spaced relationship between the frame members.

3. An insulated structure as claimed in claim 1 which includes means mounting the panels between the cover strips and the frame members but independent thereof for relative movement.

4. An insulated structure as claimed in claim 1 which includes cover plates disposed outwardly of the cover strips and dimensioned to cover the meeting intersections thereof.

5. An insulated structure as claimed in claim l which includes a continuous membrane of a iluid and vapor impervious material present as a lamina of said panels.

6. An insulated structure as claimed in claim l which includes a iluid and vapor impervious membrane covering the assembled panels and cover strips.

7. An insulated structure as claimed in claim l in which the bottom wall of said structure is formed of a relatively thick layer of a structurally strong and dimensionally stable thermal insulating material.

References Cited in the le of this patent UNITED STATES PATENTS 2,684,171 Ernst July 20, 1954 2,892,563 Morrison June 30, 1959 2,928,565 Glasoe Mar. 15, 1960 2,983,401 Murphy May 9, 1961 

1. IN THE CONSTRUCTION OF AN INSULATED SPACE OF LARGE DIMENSION FOR HOUSING ONE OR MORE CONTAINERS FILLED WITH A MATERIAL HAVING A TEMPERATURE DIFFERING WIDELY FROM AMBIENT TEMPERATURE, AN ENCLOSURE DEFINED BY A BOTTOM WALL AND VERTICALLY DISPOSED WALLS, SPACED APART FURRING STRIPS FIXED TO THE INTERNAL SURFACES OF THE VERTICALLY DISPOSED WALLS OF THE ENCLOSURE IN WHICH THE FURRING STRIPS ARE ARRANGED IN LATERALLY SPACED APART PAIRS WITH EACH OF THE FURRING STRIPS IN EACH PAIR BEING LATERALLY SPACED APART ONE FROM THE OTHER, FRAME MEMBERS SPACED INWARDLY FROM THE FURRING STRIPS AND CONNECTED TO THE FURRING STRIPS BY CROSS BRACE MEMBERS IN WHICH A FRAME MEMBER IS PROVIDED FOR EACH OF THE PAIRS OF FURRING STRIPS AND IN WHICH EACH FRAME MEMBER IS CONNECTED TO A PAIR OF FURRING STRIPS BY HORIZONTALLY DISPOSED DOWEL PINS EXTENDING OUTWARDLY FROM THE FRAME MEMBERS TO THE FURRING STRIPS, THIN PANELS OF A STRUCTURALLY STRONG MATERIAL ARRANGED IN END-TO-END AND IN SIDE-BY-SIDE RELATION AND SUPPORTED BY THE FRAME MEMBERS TO FORM A CONTINUOUS SIDING IN SPACED RELATION WITH THE ENCLOSURE WALLS TO DEFINE A STORAGE SPACE FOR SAID CONTAINERS, COVER STRIPS CONFRONTING THE INNER SURFACES OF THE PANELS TO OVERLAP THE ADJACENT EDGES AND CONCEAL ANY OPENING THEREBETWEEN, AND INSULATION MATERIAL IN THE SPACE BETWEEN THE SIDING AND THE ENCLOSURE WALLS. 